It is sometimes necessary, for example in the drilling industry, to orientate one part of a system into a predetermined angular position relative to another part of that system. For example, in the Applicant's SYSTEM FOR IN SITU REPLACEMENT OF CUTTING MEANS FOR A GROUND DRILL described in International application no. PCT/AU94/00322 (WO 94/29567) a bit locking sleeve is used to orientate a tool in a predetermined angular position relative to a drive sub connected with a lower end of a core barrel. The bit locking sleeve described in WO 94/29567 is in the form of a cylindrical tube with a pair of opposing peaks extending from one end. The tool is used for carrying bit segments to and from the drive sub and is provided with latch dogs which extend radially from the body of the tool. When the tool is lowered through the core barrel, the latch dogs contact the side faces of the peaks causing the tool to rotate about its longitudinal axis relative to the drive sub. The purpose for this is to correctly align the tool with seats and splines formed in the drive sub so that the bit segments carried by the tool can be properly located in the drive sub.
Field trials of the above system have proved very successful. Nevertheless, it is thought that there is a potential for jamming to occur between the tool and the locking sleeve. This arises because the latch dogs in the tool are provided with a small degree of play. As a result of this, if the latch dogs were to strike the very top of both peaks at the same time, there is a possibility that both latch dogs will slide to the same side of each peak causing the tool to become jammed. In order to avoid jamming, it is critical to ensure that on every occasion the latch dogs slide on opposing sides of each peak.